class Solution
{
    int m, n;
    int dx[4] = {0, 0, 1, -1};
    int dy[4] = {1, -1, 0, 0};
    bool vis[1010][1010] = { 0 };

public:
    int rotApple(vector<vector<int>> &grid)
    {
        m = grid.size() , n = grid[0].size();

        queue<pair<int,int>> q;
        for(int i = 0;i < m;i ++)
            for(int j = 0;j < n;j ++)
                if(grid[i][j] == 2)
                    q.push({i , j});
        
        int ret = 0;
        while(q.size())
        {
            int sz = q.size();
            ret ++;
            while(sz--)
            {
                auto [a , b] = q.front();
                q.pop();
                for(int i = 0;i < 4;i ++)
                {
                    int x = a + dx[i] , y = b + dy[i];
                    if(x >= 0 && x < m && y >= 0 && y < n
                    && grid[x][y] == 1 && !vis[x][y])
                    {
                        vis[x][y] = true;
                        q.push({x , y});
                    }
                }
            }
        }
        for(int i = 0;i < m;i ++)
        {
            for(int j = 0;j < n;j ++)
            {
                if(grid[i][j] == 1 && !vis[i][j]) return -1;
            }
        }
        return ret - 1;
    }
};